The present invention relates to a magnetic resonance apparatus which acquires navigator signals generated from a navigator region including body-moving portions, using a coil having a plurality of channels, and a method for acquiring navigator signals generated from the navigator region.
There has been known a body movement correction technology using navigator echoes. The body movement correction technology is effective in reducing artifacts caused by respiration, for example. When, however, the navigator echoes are acquired from the boundary between the liver and the lung, there is a case where body movement information cannot be acquired due to unnecessary signals of subcutaneous fat and the like.
To cope with the foregoing problem, there has been known a technology which acquires navigator echoes using a multicoil having a plurality of channels and selects a channel less susceptible to signals of subcutaneous fat and the like out of the channels (See, for example, Brau et al. “Evaluation of Coil Selection Algorithms for Body Navigators” ISMRM, 2012, 3407).
In Brau et al. “Evaluation of Coil Selection Algorithms for Body Navigators” ISMRM, 2012, 3407, each channel is selected using a template TI shown in FIG. 25. In the template TI, a signal value in an SI direction of a navigator region is a profile having ideal values. In the template TI (hereinafter may be called “ideal template”), the horizontal axis indicates a position i in the SI direction of the navigator region, and the vertical axis indicates a signal value Wi. A resolution in the SI direction of the ideal template TI is expressed in “res”. When res=256, for example, the resolution in the SI direction of the ideal template TI becomes 256 pixels. The ideal template TI can be generated by referring to data of plurality of profiles obtained from a plurality of healthy human bodies. In Brau et al. “Evaluation of Coil Selection Algorithms for Body Navigators” ISMRM, 2012, 3407, the ideal template TI shown in FIG. 25 is prepared, correlation coefficients between the ideal template TI and profiles obtained from respective channels are calculated. Then, channels less susceptible to the signals of the subcutaneous fat and the like are selected out of the plural channels, based on the correlation coefficients.
In the method of Brau et al. “Evaluation of Coil Selection Algorithms for Body Navigators” ISMRM, 2012, 3407, however, there is a case where the optimal channels cannot be selected when a signal in a lung region is large. There has therefore been a demand for a technology capable of selecting the optimal channels even when the signal in the lung region is large.